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Looking at some Panorama data: tempo

Last time, we looked at some of the recordings in our dataset and identified several peculiarities: spoken announcements and introductions at the beginning of recordings, sometimes lasting 10s of seconds; crowd noises throughout, and sometimes much more perceivable than the music; differences in pitch shifting between recordings; recording effects like warble. Furthermore, there are not very many well-defined markers of tempo save the countoff at the beginning of a tune. I find it very hard to tap to the beat when I select random starting positions in a recording. How will our feature extraction algorithms handle this with our recording collection?

Let’s look at tempo at this time. We use two tempo description algorithms. One is the QMUL Tempo and Beat Tracker Vamp plugin, which gives a tempo estimate whenever a change is sensed. The other is madmom tempo, which gives a tempo estimate for the entire piece.

Using Tempo Tap, I estimate a tempo of about 140 beats per minute (bpm). madmom says it’s 139 bpm. Let’s go with madmom. For this recording, the first 40 seconds is an announcement. From then to the just about the end is the music. Still, the QMUL tempo tracker is making an octave error for the majority of the recording.

Now let’s look at our recording of the 1980 performance of the Trinidad All Stars (playing “Woman on the Bass”).

Again we see octave errors in the QMUL tracker. madmom estimates a tempo of 136 bpm. I estimate it to be around 135 bpm.

Now let’s look at our recording of the 1994 performance of Desperadoes playing “Fire Coming Down”.

From what we have seen, it seems the madmom tempo is actually a reliable estimate of the tempo. Let’s look at the entire collection of tempo estimates:

Nearly all of the tempo estimates of our 93 recordings are between 115 and 140 bpm, but there are some that are suspiciously slow or fast. The slowest is the recording of the 1982 performance of Amoco Renegades playing “Pan Explosion”:

According to my tapulations, this is more like 137 bpm (our recording has a slightly slower speed and lower pitch than the video above).

The fastest tempo estimate of madmom is of the 1985 recording of the Trinidad All Stars playing “Soucouyant.” Here a video where they start playing at a tempo of around 140 bpm but end around a tempo of 145 bpm.

The performance in our recording is faster! I tapstimate it starts around 147 bpm and ends around 154 bpm. So, it seems madmom is not entirely incorrect with our recording, but the performance in our recording may not be accurate.

For the other seven supposedly slow performances I find four tempo estimates that are clearly wrong:

What about all the ones in the middle range? Should we verify all of them? Even so, what conclusions can we make about the tempo conventions considering that our recordings may not accurately reflect the practice?